During its operation a mass spectrometer may experience changing conditions which can have a significant impact upon the measurements made by the mass analyser. It is well known, for example, that temperature changes can significantly shift the measured mass to charge ratio of ions.
In order to address this problem it is known during operation of a mass spectrometer to periodically calibrate the mass spectrometer, e.g. by periodically mass analysing known lockmass or calibration ions. If the mass spectrometer determines that the measured mass to charge ratio of the known lockmass or calibration ions has shifted (or broadened) then the measured mass to charge ratio of analyte ions may be adjusted to correct for the shift, or the mass spectrometer may be adjusted in some other way.
Mass analysing known lockmass or calibration ions during operation of a mass spectrometer typically involves introducing lockmass or calibration ions into the mass analyser in place of the analyte ions. However, this gives rise to a problem in that the displaced analyte ions are then lost to the system and the analyte ions are not measured by the mass analyser. As a result, portions of the resulting mass spectral data may be degraded and/or lost.
US 2006/169883 (Wang), EP-2741312 (Knochenmuss) and WO 2014/135866 (Micromass) disclose methods for calibrating a mass spectrometer.
It is desired to provide an improved mass spectrometer and method of mass spectrometry.